(1) Field of the Invention
The present invention relates to digitally acquired radiographs and, more particularly, to a high speed, high definition navigation and display system for digital mammograms.
(2) Description of the Related Art
The American Cancer Society estimates that 44,300 women will die this year from breast cancer, which is the leading cause of cancer-related deaths among women in the United States. X-ray mammography is the only proven tool capable of detecting this cancer in its early stages. Use of x-ray mammography doubled between 1987 and 1992, and conditions appear favorable for a continuing increase. Laurie L. Fajardo, M.D., New Detectors Boost Mammographic Accuracy, Diagnostic Imaging, November 1996, at D7.
Currently, mammograms are viewed on a multiviewer 100 (also known as a viewbox) as hard copy film, as shown in FIG. 1. Images from a current examination are hung on a lower level 102 of the multiviewer, and include a right cranial-caudal ("cc") view 104, a left cc view 106, a right oblique view 108, and a left oblique view 110. The same views from a prior comparison exam are hung on an upper level 112 of the multiviewer, and include a right cc view 104', a left cc view 106', a right oblique view 108', and a left oblique view 110'. In general, the images are viewed in a systematic order, and the current images are compared to the prior images to detect any changes. Thus, a mammographer reviewing the single patient study illustrated in FIG. 1 moves his head and eyes upwardly and downwardly to compare a set of views from the current and prior examinations, such as the right cc views 104, 104'. After conducting this comparison, the mammographer shifts his head and eyes from left to right to review the next view from the current examination, such as the left cc view 106, and then again shifts his head and eyes upwardly and downwardly to compare the left cc view 106 with the left cc view 106' from the prior examination. Other arrangements of the various views can be and sometimes are employed.
These reviews are ordinarily conducted first without magnification to identify abnormalities indicative of a cancer onset, including suspicious masses, and are then repeated with a magnifying lens to identify any clustered microcalcifications, another indicator of developing breast cancer. A typical multiviewer can hold fifty or sixty patient studies (also known as panels), each comprising eight film-screens of the eight views described above, and the average mammographer can usually review a patient study in approximately one to two minutes. Although film-screen mammograms have drastically improved the ability of mammographers to detect the early signs of breast cancer, its accuracy can be improved.
Along with the other modalities for medical imaging, mammography is being propelled into the next century by progress in digital technology. Digital mammography may fundamentally change the practice of medicine, allowing the earliest signs of cancer to be detected more accurately, thereby dramatically improving patient outcomes. Specific advantages of digital mammography include the potential for better image quality, real-time display, image-enhancement capabilities, computer-assisted abnormality detection, and ease of image management and transfer (for remote interpretation). With respect to image enhancement, techniques are already known in the art for enhancing visualization of masses, microcalcifications, architectural distortions, and tissue densities.
Prototype full-breast detector systems are now available for acquiring mammograms digitally so that the images are never recorded on film. Similar systems are available for digitizing radiographs, including mammograms, from films or slides. It is presently unclear, however, how high resolution, full field of view (FOV) digital mammograms will be read. Suggested approaches include printing the digital images on laser film for viewing, the development of monitors having 4k.times.4k or greater pixel matrices, and use of head-mounted displays currently under development by the intelligence and defense community. Given the cost consciousness in the healthcare community, however, these approaches may be cost prohibitive or provide for insufficient radiologist productivity. Printing processed digital images on laser film merely compounds the high cost of film-screen radiographs with the high cost of digital receptor systems. Similarly, the high cost of monitors having 4k.times.4k pixel resolution, or head-mounted displays, can hardly be estimated at present, as such systems will be commercially unavailable for many years to come. Although digital workstations employing high definition ("HD") monitors with 1k.times.1k, or 2k.times.2k, pixel matrices have been proposed, a separate monitor is required for displaying each image in a patient study, again at a prohibitively high cost. In the case of digital mammography, a total of eight or more HD monitors would be required.
Another important issue overlooked in discussions of the future of digital mammography is how the digital workstations can permit the mammographer to navigate through a mammographic study efficiently. The various proposed approaches focus on displaying one radiographic image at a time on an HD monitor. Little if any attention has been given to how the radiologist will navigate through the images in a typical patient study, including possibly many renditions of each individual image, in an efficient manner so as to make the most cost-effective use of the radiologist's time. Continuing to overlook this issue will likely hinder the clinical acceptance of digital mammography.
What is needed is a system and method for viewing digitally acquired radiographs without requiring presently unavailable, high cost, HD monitors having 4k.times.4k or greater pixel matrices, and at speeds that make effective use of radiologists' time. Such a system and method would preferably allow a radiologist to view images on only one currently available HD monitor (i.e., having a 1k.times.1k or 2k.times.2k pixel matrix), or two at most, so as to minimize system costs. The radiologist should be able to use such a system and method in an intuitive manner so that only minimal training would be necessary. Minimizing the cost and the complexity of use of such a system, while maximizing the speed at which the images can be viewed, would facilitate its clinical acceptance, thereby promoting the progress of digital radiography and its corresponding medical advantages.